By using a new polyclonal B cell activator (PBA), i.e., Salmonella paratyphi B (SPB), B cell functions in peripheral blood lymphocytes (PBL) prepared from aged humans and patients with autoimmune disease will be determined. To further understand the abnormal immune reactivity in aged humans and autoimmune disease, the proportion of two B cell subsets (B1 and B2 cells) identified by their adherence to Staphylococcus aureus 1 will be esamined in comparison with normal adults. In order to characterize the function of each B cell subset, B1 and B2 cells will be isolated by using immobilized bacterial monolayers, and the response of each B cell subset to different PBA will be tested. Furthermore, the number of spontaneous plaque forming cells and intracytoplasmic immunoglobulin (Ig) containing cells in each B cell subpopulation will also be determined. Since monocyte-mediated suppression of SPB-induced Ig production is generally found in normal adults, it has become a useful tool for evaluating the suppressive activity of monocytes on B cells in aged human and patients with autoimmune disease. To study the mechanism of monocyte-mediated suppression, supernates from cultured monocytes will be examined to determine whether soluble suppressor factor(s) secrected by monocytes mediate this type of suppression. If a loss of suppressive monocytes is found in aged humans and patients, one of our long term goals is to explore the potential therapeutic application of the soluble suppressor factors. Since monocyte-mediated suppression of SPB-induced B cell activation could be different from monocyte-mediated help for PWM-induced B cell activation, subpopulation of monocytes will be separated and isolated by discontinuous bovine serum albumin centrifugation. Each subpopulation of monocytes will be tested for their ability to mediate help or suppression of B cell activation.